Hydronic energy metering for individual apartments

JimRafferty

Greetings,
We have a rental account with 1 gas fired boiler and 4 zoned residential apartments. 3/4" finned copper on each loop.
The landlord is looking for a way to split the utilities off to the tenants. The layout of the building won't permit 4 individual boilers.
Has anyone had any experience- good, bad or ugly- trying to meter the hydronic flow/energy consumption to individual units?
The closest we've come is when we picked up an account who was trying to clock a common oil tank in a 25 unit townhouse development. Tenants were complaining and local Weights and Measures ruled that their meters were not legal for trade.
Any thoughts or wisdom appreciated.
Thanks

GroundUp

Is it zoned with circulators or zone valves? One can certainly install BTU meters on each unit's piping to determine exact actual usage, albeit rather costly. I own quite a few rentals myself and have gone about this a few different ways. My 4 unit building is 4 completely identical 2/1 units and was zoned with circulators when I bought it. What I did there was simply install four basic digital hour meters (like would be on a golf cart or forklift) and wire them to each zone to measure run time of each circulator. The 31st of every month I drop by to inspect my building and take a reading of all 4 hour meters as well as the gas meter and do the math, then charge accordingly. It's not down to the penny accurate, but within a couple bucks.

In a 10 unit building I have, it's all in-floor radiant on a slab. I had a local nerd build me an interface using an Arduino control board which has sensors on the supply and return of each unit. The Arduino communicates via wifi to an app on my phone and I can see in real-time whenever I want what temperature anything in the building is, and the app also logs cumulative data from each unit so I know exactly how many BTU are used in each unit for any given time period. It works awesome, but it's somewhat cobbled and not very professional looking. I like that I don't have to make a site visit every month, but I also have a live-in caretaker there that would be able to take readings for me if necessary.

An actual BTU meter would be the most proper channel if someone were to take something to court with alleged overcharging, but I think either of my methods would stand up in court if it came to that. Next time I'm going to have the Arduino nerd build me another system utilizing the hour meters again so it's still basic but can be viewed and monitored remotely via wifi. Most any method is going to require some sort of flowmeter to determine actual flow rate and calculate BTU. My 4 unit being 4 identical units with the exact same emitter length and piping within 10 feet for each makes it a little less necessary but in most cases that would need to be considered along with the run time

Zman

I have several clients with these:
https://www.onicon.com/products/system-10-btu-meter/

They work very well.

rick in Alaska

I priced out a btu meter for a 4 unit apartment building, but the owner never had me do it. Been a while, but it was not cheap.
The brand I was looking at was an Istec brand. Just something else to look at for comparison.
Rick

hot_rod

There is a heat metering standard now. Any equipment that you use needs to be listed to the standard to legally bill customers. Caleffi Contaga is another option

GroundUp

"Legal" is subject to the terms of the lease agreement when talking rental property, unless certain municipalities have further requirements.

Leonard

For a flow meter I once worked on a self heated thermistor in center of a tube. Thermistor has to be self heated to hotter than fluid max temp, flow cools thermistor so can determine flow rate. A 2nd thermistor compensates for changes in fluid temp. BSME or MSME Student at Worcester Polytechnic Institute (Mass.) did his final paper on that ~ 1980, describes all the details. His was likely a room temp application, but likely will work on hot water too, just have to make sure thermistors can take the hot temp, but I suspect they can, they are basically wires stuck in a "ceramic" like material then fired. Thermistor was placed in center of pipe. Calibrated with a known actual flow. Guessing gallon jug draining in X seconds might suffice, if set it up with a long tube up to jug ( ~ constant pressure in pipe).

-------------------------------------
Maybe ? add legal wording to your lease that tenant agrees to accept your DIY meter readings as accurate and will pay you what they determine energy use is. And in case of a legal dispute they agree to reimburse you all court costs and judgments. Tenent rights under law might over ride that, but at least you make tenents think they can't win, so they might not try

My tenents have separate gas meters.

hot_rod

> @GroundUp said:
> "Legal" is subject to the terms of the lease agreement when talking rental property, unless certain municipalities have further requirements.
In some States you fall under the PSC considered a utility if you meter and bill energy. Best to check.

GroundUp

No matter the lease language, it won't override the law. But there is no federal law covering how LL can charge for heat or utilities. NY and MA I believe have their own laws on the subject, perhaps some other states, but the majority of the country relies on lease language. Mine say something along the lines of "tenant agrees to pay their share of the monthly heating bill, as documented by monthly meter readings" and is totally legally binding in my state

hot_rod

Looks like 22 States have laws regarding sub metering, it might be best to get a legal opinion. Energy meters need to be certified and sealed to be legal is my understanding. Possibly in some areas they need to be recertifeid occasionally, like gas pumps?

The MN statue seems to talk about sub metering electricity after the utilities meters, not sure how BTU meters are interpreted?


Sec. 2. Minnesota Statutes 1982, section 216B.02, is
amended by adding a subdivision to read:
Subd. 6a. "Submetering" means measuring, by a building's
owner, through mechanical or electronic devices, the use of
electricity by occupants in multiple-unit residential or
commercial buildings to fairly apportion the entire electrical
costs for the building among its occupants.
Sec. 3. [216B.022] [SUBMETERING.]
Nothing in this chapter grants the commission or a public
utility the authority to limit the availability of submetering
to a building occupant when the building is served by a public
utility's master meter which measures the total electric energy
delivered to the building.
Approved June 14, 1983

JimRafferty

Thank you all for your input.
Some of your equipment suggestions definitely look like they will do what the landlord is looking to do.
Best!

Leonard

Have some commercial property and have been to court and talked with lawyers about other stuff.

I suspect state law can easily over ride anything you write in your lease. But I'm GUESSING not all states have metering rules in place. I'm an engineer, I only fix my own heating systems.

I'ld put the wording in my lease anyways , at least gives me a chance at not having problems. Maybe good to includes words to the effect of in case of dispute tenant agrees to pay bills presented by landlord for heat/utilitys/etc, or at least agrees to reimburse him any and all losses , including legal fees, in event of a dispute, no matter how dispute is resolved.

Besides with words in lease if run into problems at least it might give your lawyer something to fight with, if it comes to that. But I'm guessing tenants don't have much money and will quickly back down when your lawyer talks to them. But not all will.

We went safe route on residential house, 2 apt , separate utility meters and furnaces. Tenant will pay utility bill since he doesn't want to freeze. And if no pay utility is stuck with the losses. A plus is don't have to do monthly billing and meter maintenance

But i realize this is not applicable in all buildings. Could ask your lawyer, but might get free advice on the subject from city or state.

Lawyer will likely give you worst case answer, buy and install a certified meter by a licensed furnace tech ( highest $$$$ option). Lawyers like being able to say things like that in court.... implies you did everything right. 3-rd party installer is less likely to bias readings to your $$$ benefit.

mattmia2

I don't think your measuring supply and return temps will give you accurate energy utilization info. Flow will vary with different combinations of zones calling, even if it is primary/secondary, any thermostatic mixing will change the head on the pump and change the flow.

Leonard

Engineering wise seems you need to know BOTH delta-temp ( supply, return) AND flow rate .

If that varies with time, then want to know those instantaneous numbers. Multiply instantaneous flow and delta-temp over "short" time segment , then sum up the results over time. To be accurate want time segment short enough that measurements don't change over that time period. ( got to engineer it right)

And add in something for furnace stand by losses, when not supplying heat to apts.

GroundUp

mattmia2 said:

I don't think your measuring supply and return temps will give you accurate energy utilization info. Flow will vary with different combinations of zones calling, even if it is primary/secondary, any thermostatic mixing will change the head on the pump and change the flow.

BTU meters measure flow and calculate actual usage. Majority of apartments are a single zone without TRV, so flow rates can be pretty easily measured one time and used as the calculation factor. If one is only measuring run time, flow rate doesn't matter because the bill gets split according to run time

hot_rod

Yes for an accurate energy/ BTU meter you need both flow and delta

The sampling rate for meters listed to the new EN 1434 is dictated by the standard, I believe

More accuracy by shorter sampling rate but the data Collection can get massive.

We did a Coffee with Caleffi regarding energy metering , achieved at the Caleffi You Tube channel